I’m about to start wiring USB socket to experiment MIDI USB. But first, I wonder where I should connect the connector shield to. Should I connect the case to GND or should I do otherwise?

I found a good thread in Electrical Engineering Stack Exchange.

tl;dr: Never connect to GND. Leave it unconnected or connect to the shield of the rig. I should take the former in my current project.

Although it’s long, this thread is pretty interesting so is worth reading.